1. Field of Invention
This invention pertains to a mobile railroad track surveying and monitoring apparatus and method, and more particularly, to a system employing High Accuracy Differential Global Positioning System receivers linkable with other non-invasive sensors for rail track superstructure and substructure surveying and monitoring. The invention is capable of modeling rail track movement, rail track vectors, rail track alignment, and subsurface conditions. The apparatus includes a mobile platform and surveying components situated for measuring accurate position data for rail alignment, rail surveying, and displacement trajectories of rail, as well as for collecting subsurface condition data. Means are additionally provided to correlate the position coordinate and subsurface condition data, display such data, record such data, and compare and model such data to previously established data sets.
2. Related Art
In the railroad industry, the precise measurement of the rail dimensional relationships, including horizontal and vertical coordinates, distances, elevations, directions, angles, and curves is especially important for boundary determinations, construction layout, surveys, and mapmaking.
Railroad tracks generally comprise a set of parallel rails upon which railroad cars or other suitably equipped vehicles run. Usually, the track consists of steel rails, secured on crossties, or “ties”, so as to keep the rails at the correct distance apart (the gauge) and capable of supporting the weight of trains. As is also understood, monorails comprise a single rail. In any event, the rails can move as a result of surface subsidence, as is common along river banks. Buckling of rails caused by temperature influences also causes changes in the horizontal and vertical track alignments. These anomalies must be identified as part of routine track maintenance. One method for locating such anomalies is to compare an initial track data set with a subsequent track data set. Differences between the data sets indicate anomalies that can then be more thoroughly investigated.
Usually, an initial baseline track data set is acquired by measuring accurate position data of rail alignment using precise surveying methods. After a time, subsequent position measurements may then be collected along the same track length. The subsequent position measurements may then be compared with the baseline data. Specifically, the corresponding vertical and horizontal coordinates from each data set are compared. This comparison of data sets collected from the same stretch of track yields information regarding rail movement.
Usually, conventional surveying techniques are employed to plot rail alignment. However, conventional surveying practices are labor intensive and produce mixed results, especially when used in areas of significant ground movement. Because such conventional surveying systems require position on stable ground, any ground movement then results in the movement of the surveying monuments as well as the rails, thereby resulting in inaccurate surveying.
Conceptually, Mobile Multi-Sensor Systems (MMS) can accurately inventory geometric data along transportation routes such as roads, rivers and railways as described in the publication “El-Sheimy, N., Mobile Multi-Sensor Systems: Final Report” (1995-1999), International Association of Geodesy, IAG Special Commission 4, July 1999. Mapping systems acquiring positional coordinate data by means of a satellite receiver are well known in the art. As discussed, real-time applications possible in principle include the integration of digital imaging sensor results and precise navigation and surveying data. Equally well known are the limitations and poor accuracy of such data where there is loss of signal reception and inadequate sensor selection or configuration. Integral to implementation of such systems, but not described in the art, is a carrier vehicle, or mobile platform, suitable for accurate, precise, and operational flexibility equipped with such precision navigation and imaging sensors configured for real-time geo-referencing applications.
Similarly, integrated navigation technologies, including Global Positioning Systems (GPS) and Inertial Navigation Systems (INS), are discussed in El-Sheimy, N., “Report on Kinematic and Integrated Positioning Systems,” TS5.1 5 Activities: Yesterday and Tomorrow, International Congress, Washington, April 2002. However, the art fails to address a mobile platform suitable for accurate, precise, and operationally flexibly equipped precision navigation and imaging sensors configured for real-time geo-referencing applications.
Comparably, a modular lightweight platform for track surveying is discussed in Wildi, T., Glause, R., “A Multisensor Platform for Kinematic Track Surveying, International Workshop on Mobile Mapping Technology”, Bangkok, April 1999. The art fails to address platform negotiations through switches, vibrations, side-to-side movement of platform, location of navigation and other sensors, antenna orientation, reduction of data dropouts, alignment of the antenna and sensors, use of a survey controller for elevation offset, vehicle wandering and vehicle speed. The art fails to identify a platform apparatus minimizing or accounting for these sources of error necessary for precision navigation and surveying in real-time applications. It fails to address a mobile platform, suitable for accurate and precise surveying as well as operational flexibility.
Additionally, an electronic track surveying car with satellite (EM-SAT) used for mechanized surveying is described in Litchberger, B. “Electronically Assisted Surveying on Plain Track and Switches with GPS Link,” 2001. EM-SAT employs laser chord technology in combination with a GPS receiver. The combination of relative laser measurement and GPS coordinates, used in EM-SAT, is also addressed in “Electronic track geometry surveying and timely spot maintenance Two key element to fully exploit heavy haul track” by Ing. Rainer Wenty. This technology, however, is dependent upon lasers in combination with GPS systems, and fails to address platform movement, vibrations, location and selection of navigation and other sensors, antenna placement for reduction of data dropouts, using a survey controller for elevation offset, vehicle wandering and vehicle speed. It fails to identify a platform apparatus minimizing or accounting for these sources of errors necessary for precision navigation and surveying in real time applications. It fails to address a mobile platform, suitable for accurate and precise surveying as well as operational flexibility.
Jan Zywiel et al. discuss in “Innovative Measuring System Unveiled,” September 2001, a modular blend of GPS systems and inertial sensors combined with optical gauge measurements to accurately measure track geometry and identify its geographic location. However, the art fails to disclose a mobile platform, suitable for accurate, precise, and operational flexibility equipped with precision surveying and imaging sensors configured for real-time geo-referencing applications.
“Ground Penetrating Radar Evaluation of Railway Track Substructure Conditions” by G. R. Olhoeft et al. discusses use of a sport utility vehicle (SUV) modified for hy-rail use to which is mounted ground penetrating radar (GPR) to image track. Specifically, antennas were mounted 19 to 22 inches above railroad ties in different electric field configurations. However, the technology is limited to GPR data and orientation of radar fields. Similarly, J. Huggenschmidt discusses GPR inspections in “Railway track inspection using GPR” which is limited in application to GPR. It neither addresses platform specifications nor sensor orientation and configuration for GPS based surveying. Additionally, G. Olhoeft describes GPR applications in “Automatic Processing and Modeling of GRP Data for Pavement Thickness and Properties.” This article, like the other GPR specific articles, is mostly inapplicable to GPS system orientation, and fails to address platform movement, vibrations, location and selection of navigation and other sensors, antenna placement for reduction of data dropouts, use of a survey controller for elevation offset, vehicle wandering and vehicle speed. The art fails to identify a platform apparatus minimizing or accounting for these sources of error necessary for precision navigation and surveying in real-time applications. It fails to address a mobile platform, suitable for accurate and precise surveying as well as operational flexibility.
Munsen has described developing GPS algorithms to precisely monitor rail position, then combine track survey and rail temperature data to infer contained rail stress to predict types of rail buckling as discussed in the “Rail Research Center and AAR Affiliates Laboratory” Vol. 6, No. 2, 2001. However, platform design, sensor configuration and orientation, and real-time applications are not addressed. Again, like the other prior art discussed herein, it fails to address platform negotiations through switches, vibrations, side-to-side movement of platform, location of navigation and other sensors, antenna orientation, reduction of data dropouts, alignment of the antenna and sensors, use of a survey controller for elevation offset, vehicle wandering and vehicle speed. The prior art universally fails to identify a platform apparatus minimizing or accounting for these sources of error which is necessary for precision navigation and surveying in real-time applications.